1. Field of the Invention
The present invention relates to a heat developing apparatus, and more precisely, to a heating apparatus which forms an image by heating a sheet-form material, which carries image data thereon.
2. Description of the Related Art
A lithographic film (a photosensitive material) has been used for a long time for printing newspaper, magazines, and the like. In the same way as a photographic film, an image can be formed on a photosensitive material such as the lithographic film, by carrying out processing (wet processing) such as developing and fixation. However, when each processing such as developing and fixation, is carried out by wet processing, the developing processing becomes complicated. Moreover, since each processing is carried out by soaking the lithographic film in processing tanks in sequence, each of which stores a processing solvent (e.g., a developer or a fixer), there has been a problem with this method in that control of each processing is troublesome, and deterioration of a heat developing apparatus itself is accelerated by dirt or the like adhering to the heat developing apparatus.
In contrast, a heat developing apparatus capable of developing processing on photosensitive materials such as the lithographic film without complicated processing (the wet processing) such as development and fixation, has been proposed. This heat developing apparatus carries out developing processing by superposing a photosensitive material, on which an image has been exposed, and an image receiving material one on top of the other, heating them for a certain period of time, and then peeling the photosensitive material from the image receiving material, and drying them (i.e., so-called dry processing is carried out).
As shown in FIG. 8, a photosensitive material 126, on which an image has been exposed by an exposure device 102 provided adjacent to a heat developing apparatus 100, is inserted into the heat developing apparatus 100 from an insertion opening 104, and is conveyed by plural transport rollers 106. A water application section 108 and a heat developing section 110 are provided along the direction the photosensitive material 126 is conveyed. At the water application section 108, water is applied onto the photosensitive material 126, so that the adhesion between the photosensitive material 126 and a processing sheet (i.e., the above-described image receiving material) 112 can be improved. A heating drum 114 is provided in the heat developing section 110. A heater 116, which is contained inside the heating drum 114, raises the temperature of the rotating heating drum, and the photosensitive material 126 and the processing sheet 112 conveyed along the outer peripheral surface of the heating drum 114 are heated for a predetermined period of time (i.e., heat developing processing is carried out). At this time, the photosensitive material 126 and the processing sheet 112, which have been superposed one on top of the other, are conveyed in a state in which they are attached by pressure. After completion of heat developing processing, the photosensitive material 126 is peeled from the processing sheet 112, and is dried by plural fans 118.
Moreover, as shown in FIG. 9, a heat developing section 110A may be structured such that plural heating plates 120A to 120E are provided in a circular arc configuration in order to restrict the height of a heat developing apparatus 100A. A flat heater (not shown) and a flat temperature sensor (also not shown) are built into the heating plates 120A to 120E, and the heating plates 120A to 120E are heated so as to be a suitable temperature for heat developing processing. That is, heat developing processing is carried out by conveying the photosensitive material 126 and the processing sheet 112, which have been laminated together, along the circular arc configuration of the heating plates 120A to 120E through a belt 124.
Therefore, since a liquid containing chemicals, such as a processing solvent, is not used, nuisances such as liquid storing, replenishment control, and apparatus cleaning can be avoided, and maintenance properties of the apparatus can be improved.
However, in the heat developing apparatus 100 shown in FIG. 8, heat developing processing is carried out by conveying the photosensitive material 126 and the processing sheet 112 along an outer peripheral surface of the heating drum 114 set in the heat developing section 110, and by attaching the photosensitive material 126 and the processing sheet 112 onto the outer peripheral surface of the heating drum 114 from pressure by a pressing belt 122. Moreover, in the heat developing apparatus 100A shown in FIG. 9, heat developing processing is carried out by conveying the photosensitive material 126 and the processing sheet 112 along the circular arc configuration of the heating plates 120A to 120E through the belt 124. That is, heat developing processing is carried out in a state in which the photosensitive material 126 and the processing sheet 112 laminated together are caused to contact with and to be attached by pressure to the heating drum 114 or the belt 124 wound around the heating plates 120A to 120E.
Accordingly, since a mechanism for causing the photosensitive material 126 and a processing sheet 112 to contact with and to be attached by pressure to the heating drum 114 or the belt 124 wound around the heating plates 120A to 120E is needed, there is a problem with this method in that the inner structure of the heat developing apparatus becomes complicated.
In the heat developing apparatus 100 shown in FIG. 8, the heater 116 is built in the heating drum 114, and the photosensitive material 126 and the processing sheet 112 are heated via the heating drum 114. Moreover, in the heat developing apparatus 100A shown in FIG. 9, the flat heater is built into the heating plates 120A to 120E, and the photosensitive material 126 and the processing sheet 112 are heated by the heating plates 120A to 120E and by the belt 124 wound around the heating plates 120A to 120E. In this way, since the conventional heat developing apparatuses 100, 100A are structured such that the photosensitive material 126 and the processing sheet 112 are heated indirectly, not only the photosensitive material 126 and the processing sheet 112, but also the heating drum 114 and the heating plates 120A to 120E need to be heated, so that a heater of a large capacity must be built thereinto. Accordingly, there is another problem in that manufacturing costs of the heat developing apparatus increase.
Further, the heating drum 114 and the heating plates 120A to 120E are cooled gradually. Therefore, there is a problem in that when heat developing processing is carried out continuously on the photosensitive material 126, the temperature of the heating drum 114 and the heating plates 120A to 120E is unstable, and it is difficult to adjust the temperature to a value suitable for heat developing processing. Moreover, there is another problem in that an uneven developing is caused by the shapes of the heating drum 114 and the heating plates 120A to 120E, so that an image cannot be formed accurately.
In contrast, there is a method for heating a photosensitive material without using the heating drum 114 and the heating plates 120A to 120E. In such a method, a heater is provided so as to face the photosensitive material conveyed linearly, so that the photosensitive material is heated by relative movement of the photosensitive material and the heater.
However, when this method is used, it takes considerable time to heat the photosensitive material. Moreover, when the heater is moved, the heater is cooled by the air flow generated around the heater, and the heating temperature of the photosensitive material becomes unstable, so that failures such as breaking of filaments or the like easily occur inside the heater. Furthermore, since a mechanism for moving the heater is needed, there is a problem in that the inner structure of the apparatus becomes complicated, and the apparatus itself becomes larger.